Digital electric power can be characterized as any power format where electrical power is distributed in discrete, controllable units of energy. Packet Energy Transfer (PET) is a new type digital electric power protocol that has been disclosed in U.S. Pat. No. 8,781,637 (Eaves 2012).
The primary discerning factor in a digital power transmission system compared to traditional, analog power systems is that the electrical energy is separated into discrete units, and individual units of energy can be associated with analog and/or digital information that can be used for the purposes of optimizing safety, efficiency, resiliency, control or routing.
As described by Eaves 2012, a source controller and a load controller are connected by power transmission lines. The source controller of Eaves 2012 periodically isolates (disconnects) the power transmission lines from the power source and analyzes, at a minimum, the voltage characteristics present at the source controller terminals directly before and after the lines are isolated. The time period when the power lines are isolated was referred to by Eaves 2012 as the “sample period” and the time period when the source is connected is referred to as the “transfer period”. The rate of rise and decay of the voltage on the lines before, during and after the sample period reveal if a fault condition is present on the power transmission lines. Measurable faults include, but are not limited to, short circuit, high line resistance or the presence of an individual who has improperly come in contact with the lines. Eaves 2012 also describes digital information that may be sent between the source and load controllers over the power transmission lines to further enhance safety or provide general characteristics of the energy transfer, such as total energy, or the voltage at the load controller terminals. Since the energy in a PET system is transferred as discrete quantities, or quanta, it can be referred to as “digital power”.
Eaves 2012 disclosed the method of modulating and demodulating a communication carrier signal on the same power lines that carry the electrical power. The technique is well known to those skilled in the industry and often referred to as “power line communications”, “power line carrier communications” or “carrier current communications”. The method disclosed by Eaves 2012 did not identify if the communication would occur during the time when the source and load devices are transferring power (transfer period) or if it would occur during the time when the source is isolated from the transmission lines (sample period).
The present invention discloses a method and apparatus for communication only during the sample period of the digital power waveform. During the sample period, the line is isolated, and there is no interference in the communications stream due to the normal transfer of power from the source to load devices. This provides the opportunity for cost-effective, robust, relatively high rate communications that minimize hardware and software requirements.
Although the present specification is focused on the application of the invention to a digital power transmission system, the disclosed method can be implemented for communication between generic devices without requiring the transfer of power.